2,394 research outputs found
A refined analysis of the Poisson channel in the high-photon-efficiency regime
We study the discrete-time Poisson channel under the constraint that its
average input power (in photons per channel use) must not exceed some constant
E. We consider the wideband, high-photon-efficiency extreme where E approaches
zero, and where the channel's "dark current" approaches zero proportionally
with E. Improving over a previously obtained first-order capacity
approximation, we derive a refined approximation, which includes the exact
characterization of the second-order term, as well as an asymptotic
characterization of the third-order term with respect to the dark current. We
also show that pulse-position modulation is nearly optimal in this regime.Comment: Revised version to appear in IEEE Transactions on Information Theor
MC-CDMA aided multi-user space-time shift keying in wideband channels
In this paper, we propose multi-carrier code division multiple access (MC-CDMA)-aided space-time shift keying (STSK) for mitigating the performance erosion of the classic STSK scheme in dispersive channels, while supporting multiple users. The codewords generated by the STSK scheme are appropriately spread in frequency-domain (FD) and transmitted over a number of parallel frequency-?at subchannels. We propose a new receiver architecture amalgamating the single-stream maximum-likelihood (ML) detector of the STSK system and the multiuser detector (MUD) of the MC-CDMA system. The performance of the proposed scheme is evaluated for transmission over frequency-selective channels in both uncoded and channel-coded scenarios. The results of our simulations demonstrate that the proposed scheme overcomes the channel impairments imposed by wideband channels and exhibits near-capacity performance in a channel-coded scenario
Multidimensional Index Modulation for 5G and Beyond Wireless Networks
This study examines the flexible utilization of existing IM techniques in a
comprehensive manner to satisfy the challenging and diverse requirements of 5G
and beyond services. After spatial modulation (SM), which transmits information
bits through antenna indices, application of IM to orthogonal frequency
division multiplexing (OFDM) subcarriers has opened the door for the extension
of IM into different dimensions, such as radio frequency (RF) mirrors, time
slots, codes, and dispersion matrices. Recent studies have introduced the
concept of multidimensional IM by various combinations of one-dimensional IM
techniques to provide higher spectral efficiency (SE) and better bit error rate
(BER) performance at the expense of higher transmitter (Tx) and receiver (Rx)
complexity. Despite the ongoing research on the design of new IM techniques and
their implementation challenges, proper use of the available IM techniques to
address different requirements of 5G and beyond networks is an open research
area in the literature. For this reason, we first provide the dimensional-based
categorization of available IM domains and review the existing IM types
regarding this categorization. Then, we develop a framework that investigates
the efficient utilization of these techniques and establishes a link between
the IM schemes and 5G services, namely enhanced mobile broadband (eMBB),
massive machine-type communications (mMTC), and ultra-reliable low-latency
communication (URLLC). Additionally, this work defines key performance
indicators (KPIs) to quantify the advantages and disadvantages of IM techniques
in time, frequency, space, and code dimensions. Finally, future recommendations
are given regarding the design of flexible IM-based communication systems for
5G and beyond wireless networks.Comment: This work has been submitted to Proceedings of the IEEE for possible
publicatio
Wireless distance estimation with low-power standard components in wireless sensor nodes
In the context of increasing use of moving wireless sensor nodes the interest
in localizing these nodes in their application environment is strongly rising.
For many applications, it is necessary to know the exact position of the nodes
in two- or three-dimensional space. Commonly used nodes use state-of-the-art
transceivers like the CC430 from Texas Instruments with integrated signal
strength measurement for this purpose. This has the disadvantage, that the
signal strength measurement is strongly dependent on the orientation of the
node through the antennas inhomogeneous radiation pattern as well as it has a
small accuracy on long ranges. Also, the nodes overall attenuation and output
power has to be calibrated and interference and multipath effects appear in
closed environments. Another possibility to trilaterate the position of a
sensor node is the time of flight measurement. This has the advantage, that the
position can also be estimated on long ranges, where signal strength methods
give only poor accuracy. In this paper we present an investigation of the
suitability of the state-of-the-art transceiver CC430 for a system based on
time of flight methods and give an overview of the optimal settings under
various circumstances for the in-field application. For this investigation, the
systematic and statistical errors in the time of flight measurements with the
CC430 have been investigated under a multitude of parameters. Our basic system
does not use any additional components but only the given standard hardware,
which can be found on the Texas Instruments evaluation board for a CC430. Thus,
it can be implemented on already existent sensor node networks by a simple
software upgrade.Comment: 8 pages, Proceedings of the 14th Mechatronics Forum International
Conference, Mechatronics 201
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